Representative Concentration Pathway (RCP)

The Union Ministry of Earth Sciences (MoES) has released the “Assessment of Climate Change over the Indian Region” Report.

Highlights of the report

  • Average surface air temperatures over India could rise by up to 4.4 degrees Celsius by the end of the century as compared to the period between 1976 and 2005, according to the MoES report.
  • The rise in temperatures will be even more pronounced in the Hindu Kush-Himalayan region where the average could reach 5.2°C.
  • The region is already highly vulnerable to climate-related variability in temperatures, rainfall and snowfall.
  • By 2100, the frequency of warm days and warm nights might also increase by 55 per cent and 70 per cent respectively, as compared to the period 1976-2005 under the RCP 8.5 scenario.
  • The incidences of heat waves over the country could also increase by three to four times. Their duration of occurrence might also increase which was already witnessed by the country in 2019.

A 100-year record

  • Between 1900 and 2018, the average temperatures of India rose by 0.7°C.
  • This rise in temperatures has been largely attributed to global warming due to GHG emissions and land use and land cover changes.
  • But it has also been slightly reduced by the rising aerosol emissions in the atmosphere that have an overall cooling characteristic.
  • The report predicts that monsoon rainfall could change by an average of 14 per cent by 2100 that could go as high as 22.5 per cent.
  • The report does not mention if this change will be an increase or a decrease but still represents variability.
  • It further says that the overall rainfall during the monsoon season has decreased by six per cent between 1950 and 2015.

Data on dry spells

  • The assessment also says that in the past few decades, there has been an increased frequency of dry spells during the monsoon season that has increased by 27 per cent between 1981-2011, as compared to 1951-1980.
  • The intensity of wet spells has also increased over the country, with central India receiving 75 per cent more extreme rainfall events between 1950 and 2015. This means that it either rains too little or too much.
  • One of the primary examples of this was the monsoon seasons of 2018 and 2019 where dry spells were broken by extremely heavy rainfall spells, creating a flood and drought cycle in many regions in India.

What is Representative Concentration Pathway (RCP)?

  • A Representative Concentration Pathway (RCP) is a greenhouse gas concentration (not emissions) trajectory adopted by the IPCC.
  • It is defined as a radiative force in watt per square metre due to the rising greenhouse gas (GHG) emissions in the atmosphere.
  • Four pathways were used for climate modelling and research for the IPCC Fifth Assessment Report (AR5) in 2014.
  • The pathways describe different climate futures, all of which are considered possible depending on the volume of greenhouse gases (GHG) emitted in the years to come.
  • The RCPs – originally RCP2.6, RCP4.5, RCP6, and RCP8.5 – are labelled after a possible range of radiative forcing values in the year 2100 (2.6, 4.5, 6, and 8.5 W/m2, respectively).
  • Since AR5 the original pathways are being considered together with Shared Socioeconomic Pathways: as are new RCPs such as RCP1.9, RCP3.4 and RCP7.

GHGs in atmosphere

  • The Earth’s atmosphere is made up of different gases. The temperature of the atmosphere depends on a balance between the incoming energy from the sun and the energy that bounces back into space.
  • Greenhouse gases (GHG) such as carbon dioxide (CO2), methane and nitrous oxide play an important role in the atmosphere.
  • They absorb some of the sun’s heat and release it back in all directions, including back to the atmosphere.
  • Through this process, CO2 and other GHGs keep the atmosphere warmer than it would be without them.
  • However, fossil fuel-run industries and other human activities add GHGs to the atmosphere. This, in turn, increases atmospheric temperature, causing global warming.

Assessing the carbon level

  • In 1958, American scientist Charles David Keeling calculated the amount of CO2 in our atmosphere.
  • When he started his measurements in 1958, the CO2 levels were around 315 parts per million (PPM).
  • When he died in 2005, the project was taken over by his son Ralph Keeling. By 2014, CO2 levels had increased to about 400 PPM.
  • With his systematic study of atmospheric CO2, Keeling became the first person to alert the world about the increasing levels of CO2 in the atmosphere.

Reasons for rising CO2 levels

  • Scientists first argued that the increasing release of methane and CO2 was due to agriculture and livestock.
  • But, with the start of the Industrial Revolution in the 18th century, the use of fossil fuels and CO2 levels rose simultaneously.
  • Nations that underwent the Industrial Revolution used huge amounts of fossil fuels and became centres of high CO2 emissions, while nations with an agrarian economy emitted less GHGs.
  • Over the years, as CO2 levels increased, it sparked off debates and arguments between the GHG-emitting rich industrial nations and the victims of global warming — the poorer nations.
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